This exceptional mineral gem consists of topaz-coloured, rosette-shaped crystals radiating from small stalagmites on a slab of limestone.
It was discovered in 1929 by Robert Peters in a gap between layers of stone, while he was working at Broadcroft Quarries. It was later bequeathed to Portland Museum by Mrs Vera Snowdon, Robert Peters’ mother.
The Natural History Museum have confirmed that the Rosette Gem is exceptional and that they have nothing similar in their collections. However, it’s not a precious or even semi-precious jewel – it is in fact composed of humble calcite but in a very unusual form.
Find out more on the rocks and pseudofossils page.